Perchlorate Reduction with Integrated Photochemical and Catalytic Processes

Perchlorate (ClO4⁻) contamination in water poses significant public health risks due to its endocrine-disrupting properties and resistance to degradation by conventional chemical treatment methods. The concerns about oxychlorine anions (ClOx⁻) also impact destruction technologies for per- and polyfluoroalkyl substances (PFAS). The stepwise reduction of ClO4⁻ often shows intriguing chemical challenges due to the unique reactivity of ClOx⁻ intermediates, which motivates innovation in process design. This study presents a two-stage treatment train combining photochemical treatment with catalytic reduction to achieve complete ClO4⁻ removal in complex water matrices. The optimized UV/sulfite+iodide (UV/S+I) system achieved efficient ClO4⁻ reduction. Surprisingly, the chlorate (ClO3⁻) intermediate is more sluggish than ClO4⁻ under UV/S+I treatment. To overcome this challenge, we integrated the H2+Mo−Pd/C catalytic process as a post-treatment and achieved rapid ClO3⁻ reduction to Cl⁻. The high performance of the treatment train is validated in practical matrices of tap water and synthetic ion-exchange resin regenerant brine. The photochemical stage also degraded nitrate (NO3⁻) and PFAS, which inhibited ClO4⁻ reduction at various levels. The treatment train overcomes individual technology limitations while maintaining robustness against the challenging water matrices, offering a practical solution to perchlorate-related scenarios that need comprehensive treatment of various pollutants.